“Some of that [vitriol] is very effectively organised by the establishment to undermine us, [but] this is the opportunity we waited for,” he said, according to the LabourList website.

“This is the opportunity some of us have been born for.”

He added: “This is about the establishment saying to you ‘how dare you elect a socialist as leader of the Labour party?'

“This is the establishment saying ‘get back in line, get back in your box’. They want to get back to a politics which is simply a rotation of the elites dominated by the City elites.”

Mr McDonnell also attacked media criticism of Mr Corbyn’s leadership on Sunday, as the Islington North MP marked 12 months in the top job.

“I actually think we'll shock you all in this coming 18 months in the way we can build up with the social movement we now have as a Labour party, build up our support, overcome the media barrage against us that's happening by using new techniques, social media, word of mouth meetings that we are doing, even convincing some of the media,” he told Radio 5 Live’s Pienaar’s Politics.

“I was brought up a Roman Catholic so I'm a great believer in the powers of conversion.”

In August Mr McDonnell, a close ally of Mr Corbyn, claimed a “rigged purge” of the Labour leader’s supporters was taking place in the party’s leadership contest.

General secretary Iain McNicol later disputed the allegations.

Mr Corbyn is the bookies’ favourite to retain the leadership ahead of rival Owen Smith.

The winner of the contest will be announced on 24 September, before the Labour party conference.